The present invention relates to a two-piece fastener having a pin and a swagable collar and, more particularly, to such a fastener having a design suitable for use where the collar tends to fall off the pin because of gravity.
Two-piece fasteners of the pin and swagable collar are well known in the art, e.g. as disclosed in U.S. Pat. No. 2,531,048 to Huck, and are often called lockbolts. The pin has a head at one end for engaging a surface of the work and a shank that protrudes from the other side of the work. Pulling grooves on the shank enable the pin to be pulled by a tool to put the work in compression. A variation of this fastener is shown in U.S. Pat. No. 4,472,096 to Ruhl, et al. This latter patent discloses a pin and swagable collar but the pin does not have pulling grooves. This type of pin is known as a stump type pin.
The protruding shank of the pin also has locking grooves. One slides the collar over the shank of the pin so that it abuts the work and is over the locking grooves. One then pulls on the pulling grooves and reacts the pulling force on a swaging tool to swage the collar into the locking grooves to form a joint.
Conventionally, the collar has a constant internal diameter for a slip fit over the pin shank. Because of the slip fit, it is difficult to keep the collar on the locking grooves when the collar is below the work because of gravity. One solution to this problem uses an elastomer in the roller to engage the locking grooves and hold the collar in position. However, this solution significantly increases the cost of manufacturing the collar. Accordingly, a reliable self-retaining collar that is inexpensive to manufacture is needed.